The Zu's have a very high efficiency of 101dB so you will hear a bit of hum, but even so, I have to be literally right at the speaker to be able to hear it. There is a slight transformer hum at Torri itself.

I have had two bad tubes that caused audible hum, hissing from the speakers but it was easy to pin point as it was only one channel, so I could swap tubes from one side to the other until I found the culprit.

What is your audio path? Try starting over with just the amp connected to the speakers and then start adding components one at a time. Also, plug everything in the same circuit if you can.

I posted earlier that when i power up the idecco, thats when the hum comes into play. It is audible when I'm right on top of it. Not that big a deal. I'll try some things as the days go by. Amp is breaking in nicely, had a good listening session Sat night, before i knew it it was 3:00am! Thanks guys.

Most of the time i have the tube in the idecco powered off as this sounds better at times. Would it still be audible powered off? Something i could look into and maybe upgrade the tube while I'm at it.

OC, not sure i follow you, what are adapter thread adapters? Should i just go with 3/8 instead of 1/4 thread? I did mention you & the superflys and Mike said 1/4 thread. I think i better call him back.